Why is evil always more visually interesting?

Not a real answer here just adding to your observation. Actors often say that playing the villain role is more interesting than playing the hero. The hero role having very set parameters. In the news tragedy attracts more readers than feel good stories,and people do unfortunately slow to rubberneck when driving passed accidents. I think that it has to do with being out of the ordinary and mundane.

Well interest varies from person to person but usually evil, dark, pain...stuff like that usually catches people's interest because it poses questions and make them want to know what's going to happen...when something is light and happy then people may say "oh that's nice" and move on.

Honestly, peace and tranquility doesn't make a good comic book. However, that doesn't have to apply in real life.